Apparatus for forming metal parts



May 29, 1956 c. A. NICHOLS El AL APPARATUS FOR FORMING METAL PARTS 2 Sheets-Sheet 1 INVENTORS /142455 1Q Nah 0L5 6,454 L. CZEt E/YGEB Tmswe A'rraems'xs Filed Feb. 5, 1952 May 29, 1956 c. A. NICHOLS ET AL 2,747,645

APPARATUS FOR FORMING METAL PARTS Filed Feb. 5, 1952 2 Sheets-Sheet 2 INVENTORS EC 0154645516? Mae 04s 4] [.7 v 6421. Lc'urm'aze 7- M QM ilnited States Extent APPARATUS FoR Forts ENG METAL PARTS Charles A. Nichols and Carl L. Clevenger, Anderson, Ind assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application February 5, 1952, Serial No. 270,074

Claims. (Cl. 153-78) This invention relates to a twisting device for twisting elongated workpieces and is particularly concerned with a device for providing a predetermined angle of twist in compressor blades and the like.

It is, therefore, the main object of the invention to provide a twisting device wherein an elongated workpiece, for example, an airfoil section as used in a compressor blade, may be twisted by passage through a pair of gap rolls wherein the workpiece is pulled through the rolls while the rolls are turned at a predetermined rate with respect to the lineal displacement of the blade therethrough.

In carrying out the above object, it is a further object to provide a fixture which comprises a pair of gap rolls geared together for concomitant rotation, wherein said rolls include a contour therebetween similar to the airfoil contour of a compressor blade, for example, and wherein the blade is held in a Workholder between said rolls and is pulled through said rolls by said workholder while the rolls are positively turned at a predetermined rate with respect to the rate of movement of the workholder.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

in the drawings:

Fig. 1 is a plan view of the fixture used in twisting the workpiece.

Fig. 2 is a fragmentary, sectional view taken on the line 2-2 of Fig. i.

Fig. 3 is a fragmentary section, taken on the line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic view of the apparatus shown in Fig. l at the start of the twisting operation.

Fig. 5 is a diagrammatic view of the fixture shown in Fig. l, at the end of the twisting operation.

Fig. 6 is an electrical hookup of the control system for the fixture shown in Fig. l.

A fixture or" this type may be used in the manufacture of compressor blades to provide a twist in the blades as shown and described in copending application, Serial No. 270,073, filed concurrently herewith.

in the twisting of longitudinal workpieces, for example, airfoil sections, as used for compressor blades in turbo jet engines and the like, dificulty is experienced in obtaining a uniform twist in conventional die equipment. Furthermore, such die equipment may leave blemishes and mars on surfaces of the airfoil section, which blemishes are so minute as to be substantially incapable of measurement. However, these same blemishes are quite visible to the eye and therefore are not desirable. Various fixtures have been proposed for twisting these airfoil sections and in each and every case, difficulty has been experienced in uniformity or in the marring of the blade surface. Furthermore, conventional twisting equipment is necessarily custom-built and therefore requires a completely new set of tools for every twist angle desired.

In the apparatus to be described hereinafter, any desired twist, as limited by factors mentioned herein, may be'imparted to a blade by the change of a cam surface. Also the machine per se is useful for a wide variety of blades with minor part changes that may be quickly made.

Referring specifically to Fig. 1, one embodiment of the present invention is shown wherein an immovable carrier 20 is fastened to a cross head 22 which carries tracks 24 therein, which tracks guide two roll carriers 26 and 28. The roll carriers 26 and 23 are identical but are positioned in opposed relation to one another. Each carries bearings for rolls 3i? and 32, respectively, which rolls include gears 34 fixedly associated therewith. The rolls 39 and 32 are contoured on their surfaces as at 35 and 38 to conform with the airfoil section of the compressor blade to be twisted. Gears 34'mesh with idlers 40 which connect the gears for proper direction of rotation with a pair of rack members 42. The rack members 42 are held by guide rods 44 attached to a movable piston or a ram 46 which is supported within the carrier 2i). One end of the ram 46 consists of a workpiece holder 48 having a transverse groove 5i? therein to accommodate a foot section 52 of a blade 54. This groove 56 is not a tight fit with the foot 52 but is preferably a relatively loose iit therewith so that the blade may be readily inserted and removed from the workholder 48 Mounted on the ram 46 is a roller pin 56 which rides in a camming groove or slot 58 in a cover plate 60 attached to the immovable carrier 26. The ram 46 is also attached to a movable carriage 62 which is actuated preferably by hydraulic means, not shown, and positioned beneath the carrier 2 The roll carriers 26 and 28 are mounted for axial movement along the cross head track 24 and are attached through levers 64 pivoted, as shown, to actuating cylinders 66, mounted at either end of the cross head 22. As the mechanism of cylinders 66 is in retracted position, as shown in Fig. l, the carriers 26 and 23 re maintained to their outward position on the cross head 22 whereby the rolls 3% and 32 are apart. When the mechanism of the cylinders 66 is actuated to the opposite position, the rolls move toward one another as shown in Figs. 4 and 5, whereby they are in close association with only sufficient clearance to permit a blade section 54 to pass therebetween. in this instance, any clearance may be obtained according to the adjustments made with respect to the levers and movement of the mechanism or the cylinders 66. We prefer to have a clearance in the order of about .094 of an inch over the thickness of the blade between the roll surfaces. However, this may vary as stated before if desired.

In the operation of the device, a blade 54 has its foot 52 placed in slot while the mechanism is in the position shown in Fig. l. The cylinders 66, controlling the position of carriers 26, are then actuated to cause the carriers to move inwardly towards one another so that the rolls are in proper position with respect to'the blade 54 (see Fig. 4). The actuating means for the ram 46 is then set into operation to cause the ram 46 to move rearwardly and to also rotate in the direction of the arrow shown in Fig. 4 as occasioned by the action of the camming surface 53 on pin 55. As this rotation occurs, the ram is simultaneously retracted to a position shown in Fig. 5, whereupon the blade is twisted. During this movement, the racks 42 are simultaneously moved, since they are carried by the ram 46, and through idlers 40 and gears 34, the rolls 30 and 32 are positively turned at a predetermined rate of travel with respect to the rate of travel of the blade. v'hen the mechanism reaches the position shown in Fig. 5, the blade is twisted and the cylinders 66 may then be reversed in operation to cause the retraction of roll carriers 26 and 23 whereby the blade may be removed from the workholder and the holderzis moved to the forward position again as shown in'Fig. 1, for the next operation. Each operation is a repetition of the sequence herein explained.

It will be noted that microswitches M81 and M82 are provided and are fixedly mounted to the immovable carrier and actuated by adjustable screws 70 carried by rods 44 to control the operation of the rani 46 when the rolls and 32 are in proper position. A microswitch MS3, mounted on one of the cylinders 66, controls movement of the ram in the other direction and is actuated by the bracket for the screw 70. It will be noted that two switches are provided for inward travel, namely, M81 and M82 since it is important that the operation of the device with respect to the twisting movement is not started or initiated until the rolls are bothv in proper position. Thus these two switches, which are in series, must both be closed before the ram can be actuated, thereby assuring that both rolls 30 and 32 are in position. On the retraction of the roll carriers 26 and 28, however, only one switch MS3 is used since there is no critical factor involved. Rearward movement of the ram to its limit actuates a fourth microswitch MS4 fixedly mounted to the carrier section 20 and engaged by an adjustment screw 72 at the end of the ram to cause the cylinders 66 to reverse. A detailed account of the electrical hookup for the controlling device will be set forth hereinafter. I

The rolls 30 and 32 are cut away so that the periphery is only about 270 to provide a gap to facilitate loading of the workholder. The diameter of the rolls may vary considerably and is preferably such that the peripheral dimension of each roll is substantially equal to the length of the blade being twisted. When this is possible, the racks and gears are so arranged that the rolls turn at the identical rate of surface travel as the ram, whereby no relative movement is noticed between the blade and the rolls. However, the diameter of the rolls limits the twist because no more twist can be placed in a blade than that twist which brings the edges of the blade tangent to the peripheries of the rolls. Thus, it is sometimes necessary to use rolls of smaller diameter in order to obtain a considerable twist in the blade. In this instance, the gearing of the racks and pinions involved is regulated so that a minimum of relative movement is obtained between the blade and the rolls. For example, if the length of the blade to be twisted is equal to two times the circumference of the outer portion of the rolls, then the rolls must turn so that their lineal speed on the circumference thereof is one-half of the speed of the blade whereby a slip is obtained.

All of these factors. may be predetermined in accordance with the twist desired, the length of the blade, etc., and may be easily regulated by any one skilled in the art bya change in gearing to obtain the desired results. In all'instances, the roll surfaces are contoured so as to be substantially identical to the airfoil section being twisted. In this connection, if a slip between the blade and the rolls is necessary, a more or less composite contour must be provided on the roll surfaces.

The clearance between the groove 50 in the workholder 48 and the foot 52 of the blade and the clearance between the blade 54 and the surfaces of the rolls 30 and 32 is quickly taken up as the ram 46 commences to twist whereby close tolerances are not necessary nor desirable. In place of groove 50, the workholder 48 may be provided with hydraulically or mechanically operated jaws for gripping the workpiece or the foot of the blade and such variations are fully comprehended to be within the scope of the invention. Similarly, the movement of the several parts of the device may be accomplished by gearing instead of levers or by mechanical means instead of hydraulic means as is desired, the main features of theinvention being a device which positively V twists and pulls the blade while simultaneously moving the rolls in a positive manner with respect to the movement of the blade. All of the hydraulic cylinders discussed herein may be actuated from a common source of pressurized fluid, maintained by suitable means.

Referring to the control circuits for the device, a wiring diagram for one of such circuits is shown in Fig. 6 wherein the power line enters at 100 through a main switch 102 properly fused at 104. One side of the line then passes through a normally closed push button switch PB]. to the control portion of the circuit. In starting the device, normally open push button PBZ is depressed to close the circuit through normally closed microswitch MS4 to energize relay coil R1 which closes contacts Rcl and Rcl. This establishes a holding circuit around the push button switch PB2 so that the button may be released. Closure of contacts Rcl energizes a solenoid.

valve SVI which causes the cylinders 66 to be actuated to move the rolls 30 and 32 towards one another. When the rolls are in the proper position and at the end of the stroke, the associated screws 70 close the normally open microswitches MSl and M82. This completes a circuit through microswitch MS3, which closes as soon as the rolls begin to move, to energize relay coil R2 and cause contacts R02 and. R02 to close. Closure of contacts RC2 completes a holding circuit around microswitches M81 and M82 while closure of contacts R02 energizes a solenoid valve SV2 causing the ram cylinder (not shown) to be actuated to move the ram 46 away from the rolls 30 and 32 and thus twist the blade. When the ram reaches the end of its movement, screw 72 opens normally closed microswitch MS4 to break the circuit to relay R1 which causes contacts Rel and Rcl to open, deenergizing solenoid valve SVl whereby the cylinders 66 are reversed in operation to move the rolls away from one another to the starting position, whereupon closed microswitch MS3 is opened to deenergize relay R2 causing contacts R02 and Rc2 to open. This breaks the circuit to solenoid valve SV2 whereupon the ram cylinder reverses and moves the ram back to the starting position and simultaneously causes microswitch MS4 to close.

The holding circuit through contacts RC2 is established to permit the ram to return to starting position. Push button FBI is a safety switch, if opened at any time the circuit is deenergized and the entire apparatuswill be returned to starting position by the biased hydraulic cylinders.

While the embodiments of the present inventionas herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted. a

What is claimed isas follows:

l. A twisting device for producing a predetermined angle of twist in an elongate workpiece, comprising; a pair of rolls movable towards and away from one another, means for causing said rolls to move toward and away from-one another whereby said rolls are adapted to hold a workpiece therebetween when moved towards one another, a workpiece holder retractable from a point adjacent said rolls a distance at least equal to the length of that portion of the workpiece to be twisted, means for concomitantly rotating said rolls,-rneans for retracting said holder in positivelineal relation to the speed of rotation of the rolls and a camming surface having a predetermined pitch corresponding to the desired angle of twist to be imparted to said blade, said surface being associated with said holder for efiecting rotative movement of the holder during retraction thereof.

2. A twisting device for producing a predetermined angle of twist in an elongate workpiece, comprising; a pair of opposed gap rolls adapted to engage a workpiece therebetween, means for moving said rolls towards one another so that they will engage said workpiece, a holder for holding the workpiece at one end thereof, said holder being retractable from a point adjacent the said rolls to a point at least equal to the length of a portion of the workpiece to be twisted, means for retracting the holder, a cam carried by said. holder, a cam surface. cooperating there with and causing said holder to twist during its retraction for imparting a twist to the workpiece.

3. A twisting device for producing a predetermined angle of twist in an elongate workpiece, comprising in combination; a pair of gap rolls adapted to hold a workpiece therebetween, a pair of roll holders movable at substantially right angles to the longitudinal axis of the workpiece whereby the rolls may be retracted away from the workpiece or moved into engaging relation thereto, a workpiece holder for gripping a portion of said workpiece which is not to be twisted, power means for moving said workpiece holder axially thereof from a point adjacent said rolls to a point remote therefrom, and cam means for rotating said workpiece holder during its movement through a predetermined angle of rotation, said cam means comprising a cam and a cooperating cam slot.

4. The device as claimed in claim 3, including control means for preventing operation of the power means until said rolls and roll holders are in position for engaging the workpiece.

5. The device as claimed in claim 3, including control means for preventing operation of the power means until said rolls and roll holders are in position for engaging the workpiece, and a second control means for moving said roll holders away from the workpiece when the power means has retracted the workholder to its limit of movement away from said rolls.

References Cited in the file of this patent UNITED STATES PATENTS 127,436 Smith June 4, 1872 651,748 Dierdortf June 12, 1900 656,180 Downie Aug. 21, 1900 680,903 Wiley Aug. 20, 1901 1,891,831 Okochi Dec. 20, 1932 

